Gas-filled surge arresters operate according to the gas-physical principle of the arc discharge. The surge arrester behaves electrically like a voltage-dependent switch. As soon as the voltage applied between anode and cathode of the surge arrester exceeds the level of an ignition or response voltage, an arc forms within fractions of a second in a gas-tight discharge space of the surge arrester. The high current-carrying capacity and the virtually current-independent running voltage of the arc short-circuit the overvoltage. After the influencing has subsided, the surge arrester extinguishes and the internal resistance reassumes its original operating state with several 100 MΩ.
During the rise of the input voltage between anode and cathode of the surge arrester until the level of the response voltage is reached, virtually no current flows through the surge arrester. After the surge arrester has ignited, the voltage collapses to the so-called corona running voltage, which has a level of between 70 V and 200 V for example in the case of a current of a few 10 mA to approximately 1.5 A, in the corona region. The transition to the arc discharge takes place as the current rises further in the surge arrester. The extremely low arc running voltage which is characteristic of this region, and which is between 10 V and 35 V, for example, is independent of the current within wide limits. As the overvoltage decreases, the current in the arc is depleted until the level of a minimum current of the surge arrester required for maintaining the arc discharge is undershot. The arc discharge breaks down and the surge arrester extinguishes after passing through the corona phase.
Prior to real construction of an electrical circuit in hardware, it is helpful to simulate the behavior of the circuit in order to detect errors in the circuit design or to optimize the circuit. Circuit simulation programs, such as PSpice, for example, comprise models or libraries for simulating a multiplicity of electrical components. However, simulating the behavior of a gas-filled surge arrester or a spark gap is not possible, or is possible only to a limited extent, at the present time.